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Name: _______________
Class: _______ (
)
Baptist Lui Ming Choi Secondary School
F.6 Mock Examination (2011-12)
Combined Science - Chemistry
Date: 20/2/2012
Time: 8:40–10:20a.m.
INSTRUCTIONS
1.
There are TWO sections, A and B, in this Paper. Section A carries 24 marks and Section B
carries 56 marks. You are advised to finish Section A in about 30 minutes.
2.
Section A consists of multiple-choice questions in this question book, while Section B contains
conventional questions printed separately in Question-Answer Book B.
3.
Answers to Section A should be marked on the Multiple-choice Answer Sheet while answers
to Section B should be written in the spaces provided in Question-Answer Book B. The
Answer Sheet for Section A and the Question-Answer Book for Section B must be handed in
separately at the end of the examination.
4.
An asterisk (*) has been put next to the question where effective communication is assessed.
5.
A Periodic Table is printed on the back of the Question-Answer Book B. Atomic numbers and
relative atomic masses of elements can be obtained from the Periodic Table.
SECTION A (MULTIPLE-CHOICE QUESTIONS)
1. In an experiment, one mole of hydrocarbon reacts completely with one mole of hydrogen gas
in the presence of a heated catalyst. Which of the following may be the formula of the
hydrocarbon?
A. C5H10
B.
C5H11OH
C. C5H12
D. C9H20
2. Which of the following statements about ethanol is correct?
A. It changes orange acidified potassium dichromate solution to green.
B.
C.
D.
It reacts with sodium carbonate solution to give carbon dioxide.
There is effervescence when a piece of magnesium ribbon is put in it.
It turns blue litmus paper red.
3. Which of the following is NOT a covalent substance?
A. NH3
B.
NH4Cl
C. I2
D.
SiO2
P.T.O.
Form 6
Combined Science - Chemistry
P.2
4. Given 28.6 g of ethyl ethanoate are obtained from 23 g of ethanol during the esterification
with ethanoic acid. What is the percentage yield of the ester in the reaction?
A. 81.56%
B.
75%
C. 65%
D. 54.79%
5. Consider the following compounds:
Compound X
Compound Y
Which of the following statements about the above two compounds is correct?
A. Both compounds have the same boiling point.
B. Both compounds can turn pH paper to red.
C. Both compounds have the same molecular formula.
D. Both compounds have the same odour.
6. Chlorine has a relative atomic mass of 35.5 and has two isotopes with relative isotopic masses
of 35 and 37. Which of the following statements about chlorine are CORRECT?
(1) The isotopes have same atomic number.
(2) It contains the two isotopes, chlorine-35 and chlorine-37, in a ratio of 1:3.
(3) The two isotopes have same reactivity.
A. (1) and (2) only
B.(1) and (3) only
C.(2) and (3) only
D.(1), (2) and (3)
7. The chloride of a metal X has the formula XCl3 and contains 65.6% by mass of chloride. Find
the relative atomic mass of X.
A.
27.0
B.
55.8
C.
69.7
D.
203
8. When 10.6 g of anhydrous sodium carbonate was added to 200.0 cm3 of 1.0 M sulphuric acid
at room conditions, the reaction stopped in 40 seconds. At the same time, 2400 cm3 of carbon
dioxide was produced. Which of the following statements about the reaction is INCORRECT?
A.
B.
C.
D.
The average rate of decrease in mass of sodium carbonate was 15.9 g min1
The average rate of decrease in concentration of the acid was 0.0125 mol dm3 s1
The average rate of increase in volume of carbon dioxide was 60 cm3 s1
Sodium carbonate and sulphuric acid just reacted completely.
To be continued
Form 6
9.
Combined Science - Chemistry
After the addition of marble chips to an
excess of dilute hydrochloric acid in a conical
flask, each of the following was measured
and plotted against time on a graph.
If the reaction was complete in 2.5 minutes,
which of the following, when plotted against
time, would give a graph like the one shown
above?
A.
B.
C.
D.
P.3
Time
(min)
Total mass of the conical flask and its contents
Volume of carbon dioxide produced
pH of the solution
Temperature of the solution
10. Which of the following equations represents a reaction which is impossible to take place?
A.
B.
Cu(OH)2 + H2SO4  CuSO4 + 2H2O
CuO + 2HNO3  Cu(NO3)2 + H2O
C.
D.
Cu + 2HCl  CuCl2 + H2
CuCO3 + 2CH3COOH  (CH3COO)2Cu + H2O + CO2
11. Gas U is bubbled into a solution of V as
shown in the diagram. There is a reaction
between U and the solution of V. Which of the
following combinations about U and V is
correct?
U
solution of V
U
V
A.
Sulphur dioxide
Sodium hydroxide
B.
Oxygen
Sodium hydroxide
C.
Chlorine
Potassium sulphate
D.
Hydrogen
Sodium iodide
P.T.O.
Form 6
Combined Science - Chemistry
P.4
12. Solution A is an aqueous solution with pH 3 while solution B is an aqueous solution with pH
1. How does the [H+(aq)] in solution A compare with that in solution B?
A. The [H+(aq)] in solution A is three times greater than the [H+(aq)] in solution B.
B. The [H+(aq)] in solution A is one third of the [H+(aq)] in solution B.
C.
The [H+(aq)] in solution A is
1
of the [H+(aq)] in solution B.
10
D.
The [H+(aq)] in solution A is
1
of the [H+(aq)] in solution B.
100
13. Which of the following reagents can decolourize acidified potassium permanganate solution?
(1) Na2SO3(aq)
(2) Fe(NO3)3(aq)
(3) KI(aq)
A. (1) and (2) only
B. (1) and (3) only
C. (2) and (3) only
D. (1), (2) and (3)
14. Which of the following underlined species have an oxidation number of +2?
(1)
PbO
A. (1) only
B. (1) and (3) only
C. (2) and (3) only
D. (1), (2) and (3)
(2)
Mg
(3)
[CuCl4]2
15. A white solid dissolves in water to form an acidic solution. The solution reacts with aqueous
sodium hydroxide on heating to give a gas. The solid is probably
A. calcium oxide.
B. sodium carbonate.
C. ammonium chloride.
D. sodium chloride.
To be continued
Form 6
Combined Science - Chemistry
P.5
16. Which of the following statements is/are CORRECT when zinc nitrate solution is added to
iron(II) sulphate solution?
(1) Colour of iron(II) sulphate solution becomes paler.
(2) White precipitate is given out.
(3) Zinc displaces iron since zinc is more reactive than iron.
A. (1) only
B. (1) and (3) only
C. (2) and (3) only
D.
(1), (2) and (3)
17. Given that:
P4(white) + 5O2(g)  P4O10(s)
P(red) +
5
1
O2(g) 
P4O10(s)
4
4
ΔH 1 = 2983.2 kJ mol1
ΔH 2 = 738.5 kJ mol1
Which of the following statements concerning the conversion of white phosphorus to red
phosphorus is/are correct?
A.
(1) The reaction is exothermic.
(2) Temperature of the surroundings decreases.
(3) The enthalpy of red phosphorus is relatively higher than that of white phosphorus.
(1) only
B. (2) only
C. (1) and (3) only
D.
(2) and (3) only
18. Which of the following equations represents the standard enthalpy change of formation of
hydrogen bromide?
A.
H2(g) + Br2(g)  2HBr(g)
B.
H2(g) + Br2(l)  2HBr(g)
C.
1
1
H2(g) +
Br2(g)  HBr(g)
2
2
D.
1
1
H2(g) +
Br2(l)  HBr(g)
2
2
P.T.O.
Form 6
Combined Science - Chemistry
P.6
19. Which of the following statements concerning urea-methanal is correct?
A. It is a thermosetting plastic.
B. It melts in boiling water.
C. It is usually used instead of glass.
D. It is an addition polymer.
20. Which of the following statements concerning the electrolysis of sodium nitrate solution using
graphite electrodes are CORRECT?
(1) Na+(aq) ions are preferentially discharged at the cathode to form Na(s).
A.
B.
C.
D.
(2) OH(aq) ions are preferentially discharged at the anode to form O2(g).
(3) The concentration of the sodium nitrate solution remains unchanged after
electrolysis.
(1) only
(2) only
(1) and (2) only
(2) and (3) only
21. Which of the following equations represents a practicable way of preparing the salt
underlined?
A.
B.
C.
D.
Mg(OH)2 + Na2SO4  MgSO4 + 2NaOH
NH3 + HNO3  NH4NO3
Cu + H2SO4  CuSO4 + H2
AgCl + NaNO3  NaCl + AgNO3
22. Rubidium(Rb) and indium(In) are both metals in Period 5. Which of the following statements
concerning rubidium and indium are CORRECT?
(1) Indium reacts with chlorine gas more readily than rubidium.
(2) They are very good conductors of heat.
(3) They both have five occupied electron shells.
A.
(1) and (2) only
B.
(1) and (3) only
C.
(2) and (3) only
D.
(1), (2) and (3)
To be continued
Form 6
Combined Science - Chemistry
P.7
Directions: Each question below (Questions 23 to 24) consists of two separate statements. Decide
whether each of the two statements is true or false; if both are true, then decide
whether or not the second statement is a correct explanation of the first statement.
Then select one option from A to D according to the following table:
A.
B.
Both statements are true and the second statement is a correct explanation of the first
statement.
Both statements are true and the second statement is NOT a correct explanation of the first
C.
D.
statement.
The first statement is false but the second statement is true.
Both statements are false.
First Statement
Second Statement
23. Sulphur does not conduct electricity.
Sulphur is a solid at room conditions.
24. No energy is absorbed or released in a
physical change.
Physical changes do not involve breaking of
bonds.
END OF SECTION A
Name: _______________
Class: _______ (
)
Baptist Lui Ming Choi Secondary School
F.6 Mock Examination (2011-12)
Marks:____________
Combined Science - Chemistry
Time: 8:40–10:20a.m.
SECTION B (QUESTION-ANSWER BOOK)
Answer ALL questions. Write your answers in the spaces provided.
1. (a) A sodium hydroxide solution has been exposed to air for a long time. When dilute
hydrochloric acid is added to it, colourless gas bubbles are given out. Explain the
observation with the help of equations.
(4 marks)
(b) Suggest a chemical test to distinguish each of the following pairs of solutions. Each test
should include the reagent(s), the expected observation with each compound and the
chemical equation(s)
(i)
Sodium chloride solution and sodium iodide solution.
(ii)
Magnesium nitrate solution and ammonium nitrate solution.
(6 marks)
P.T.O.
Form 6
Combined Science - Chemistry
P.2
2. (a) Scientists believe that liquid hydrogen could be a substitute for fossil fuel in future.
(i)
Liquid hydrogen is used as a fuel in space shuttles now. Explain why liquid, but not
gas, is used.
(ii)
Suggest a method to obtain hydrogen from sea water.
(2 marks)
(b) The following diagram shows a hydrogen-oxygen fuel cell.
O2 outlet
H2 and H2O
outlet
O2 inlet
H2 inlet
anode
cathode
alkaline electrolyte
(i)
Point out TWO mistakes in the diagram and correct them.
(ii)
Suggest a metal for making the electrodes of the fuel cell.
(3 marks)
To be continued
Form 6
Combined Science - Chemistry
P.3
3. Polystyrene can be produced by the set-up shown below.
water out
A
water in
a solution of styrene in kerosene
anti-bumping granule
heat
(a) State the function of kerosene in this experiment.
(b) State the function of apparatus A.
(c) Write a chemical equation for the formation of polystyrene.
(d) Explain whether polystyrene is suitable for making electrical sockets.
(4 marks)
P.T.O.
Form 6
Combined Science - Chemistry
P.4
4. Compound P has 60% of carbon, 13.33% of hydrogen and 26.67% of oxygen by mass. P can be
converted to an alkanoic acid Q with the same number of carbon atoms. Q can be converted to a
salt R by reacting with sodium hydroxide. P reacts with Q to give compound S which has a
pleasant smell.
(a) If the molecular mass of P is 60, what is its molecular formula?
(b) Give the IUPAC name of Q.
(c) What are the reagents and conditions for the conversion of P to Q?
(d) Write a chemical equation for the formation of R.
(e) Give the IUPAC name of S.
(f)
Suggest one daily use of S.
(8 marks)
To be continued
Form 6
Combined Science - Chemistry
P.5
5. In an experiment to determine the concentration of ammonia solution, 25.00 cm3 of the
ammonia solution was transferred into a conical flask and titrated against 0.1 M sulphuric acid.
A few drops of indicator were added. The titration results are listed in the table below:
Final reading (cm3)
Initial reading
(cm3)
1
2
3
4
15.90
16.70
18.40
18.50
0.00
1.50
3.10
3.40
(a)
Which indicator is suitable for this titration?
(b)
What would be the colour change of the indicator at the end point?
(c)
Write a chemical equation for the reaction between ammonia solution and sulphuric acid.
(d)
(i)
Calculate the reasonable average volume of sulphuric acid used.
(ii)
Calculate the molarity of ammonia solution.
(7 marks)
P.T.O.
Form 6
Combined Science - Chemistry
P.6
6. Liquid hydrazine, N2H4, is sometimes used as a rocket propellant.
(a) Write an equation for the formation of liquid hydrazine from its elements with state
symbol.
(b)
Given that:
1
N2(g) + O2(g)  NO2(g)
2
ΔH1
1
O2(g)  H2O(g)
2
ΔH2
H2(g) +
N2H4(l) + 3O2(g)  2NO2(g) + 2H2O(g)
ΔH3
Using the above data to construct the enthalpy change cycle and determine the enthalpy
change of formation of liquid hydrazine in terms of ΔH1, ΔH2 and ΔH3.
(c)
In a rocket, liquid hydrazine is reacted with liquid hydrogen peroxide to produce nitrogen
and water vapour. Write a balanced equation for this reaction.
(d)
Which element in the reaction in (c) is reduced? Explain briefly.
(7 marks)
To be continued
Form 6
7. (a)
Combined Science - Chemistry
P.7
Consider the following reaction involving propanone and iodine with acid catalyst:
H+
CH3COCH3 + I2
CH3COCH2I + H+ + IThe reaction progress is monitored by titrimetric analysis. At 5-minute intervals, 25.00
cm3 of the reaction mixture is transferred into a beaker and a fixed amount of excess
standard sodium hydrogencarbonate solution is added to it immediately.
(i)
What is the purpose of adding excess standard sodium hydrogencarbonate solution
to the reaction mixture?
(ii)
Name the apparatus used to accurately measure 25.00 cm3 reaction mixture.
(iii)
State ONE alternative way instead of adding excess standard sodium
hydrogencarbonate solution to the reaction mixture.
(4 marks)
(b)
The student used the experimental set-up below for purifying copper.
(i)
State any observable change
on copper electrode A.
KNO3(aq)
CuSO4(aq)
zinc
copper
copper
electrode A
(ii)
copper
electrode B
The student observed that there was no colour change in the copper(II) sulphate
solution. Explain why.
(3 marks)
P.T.O.
Form 6
8. (a)
Combined Science - Chemistry
P.8
Doctors suggest that it is better to use magnesium hydroxide as the active ingredient of
antacid tablets rather than calcium carbonate.
(i)
Write the equations for the reaction between acid and the TWO antacids
respectively.
(ii)
Suggest ONE reason for the preference.
(3 marks)
* (b)
Except for the application in (a), briefly describe TWO other applications of
neutralization with suitable examples.
(5 marks)
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_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
END OF PAPER
Form 6
Combined Science - Chemistry
P.9
Baptist Lui Ming Choi Secondary School
F.6 Mock Examination (2011-12)
Suggested Answers
Combined Science - Chemistry
SECTION A (MULTIPLE-CHOICE QUESTIONS)
01
02
03
04
05
06
07
08
09
10
00
A
A
B
C
C
B
B
D
D
C
10
A
D
B
B
C
A
A
D
A
B
20
B
C
B
C
SECTION B (QUESTION-ANSWER BOOK)
1. (a) Sodium hydroxide solution reacts with carbon dioxide gas [1] in air to form sodium
carbonate: 2NaOH(aq) + CO2(g)  Na2CO3(aq) + H2O(l) [1] The sodium carbonate
formed reacts with dilute hydrochloric acid [1] to give colourless bubbles of carbon
dioxide gas: Na2CO3(aq) + 2HCl(aq)  2NaCl(aq) + CO2(g) + H2O(l) [1]
(b) (i) Reagent: silver nitrate solution or bromine water [1]
Result: NaCl gives white ppt. while NaI gives yellow ppt. [1]or
Colourless NaI turns brown while no observable change in NaCl
(ii)
Equation: Ag+ + Cl-  AgCl while Ag+ + I-  AgI [1] or
Br2 + 2I-  2Br- + I2
Reagent: KOH(aq) or NaOH(aq) [1]
Result: Magnesium nitrate gives white ppt. while ammonium nitrate does not [1]
Equation: Mg2+ + 2OH-  Mg(OH)2
2. (a) (i)
(ii)
(b) (i)
[1]
Liquid occupies a much smaller volume than gas does. [1]
Electrolysis. [1]
There is no need to connect the circuit to a power supply. Instead, the power supply
should be replaced by a voltmeter. [1]
The positions for feeding in hydrogen and oxygen are incorrect. Hydrogen is fed
(ii)
into the anode compartment and oxygen is fed into the cathode compartment. [1]
Nickel [1]
P.2
3. (a) It acts as a solvent or a catalyst. [1]
(b) It is used to condense vapour formed from the mixture during heating, thus preventing the
escape of vapour. [1]
(c)
n
H
H
C C
C C
H H
H H
n
[1]
(d) It is not suitable because it melts or softens when hot. [1]
4. (a)
C:H:O =
60
13.33
26.67
:
:
12
1
16
= 5 : 13.33 : 1.67
= 3 : 8 : 1 [1]
The empirical formula is C3H8O.
Molecular mass = [3(12) + 8 + 16] n
60 = 60n
n=1
Molecular formula is C3H8O. [1]
(b) Propanoic acid [1]
(c) Reagent: acidified potassium permanganate solution/acidified potassium dichromate [1]
Condition: heating under reflux [1]
(d) CH3CH2COOH + NaOH → CH3CH2COO-Na+ + H2O [1]
(e) Propyl propanoate [1]
(f) It is used as a solvent / artificial flavouring / to make perfume/cosmetics (any one) [1]
5. (a) Methyl orange [1]
(b) Yellow to orange / yellow to red [1]
(c) 2NH3 + H2SO4 → (NH4)2SO4 [1]
(d) (i)
(ii)
(16.70  1.50)  (18.40  3.10)  (18.50  3.40)
 15.20cm 3 [1]
3
No. of moles of NH3
Molarity of NH3 =
= 2  no. of moles of H2SO4 [1]
= 2  0.1  15.2  10-3
= 3.04 10-3 mol [1]
3.04  10 3
= 0.1216 M [1]
25  10 3
P.3
6. (a) N2(g) + 2H2(g) → N2H4(l) [1+1]
(b)
ΔH f [N2H4(l)]
N2(g) + 2H2(g)
+2O2(g)
2 × ΔH1
+O2(g)
2 × ΔH2
N2H4(l)
+3O2(g)
ΔH3
Balanced equations: [1]
State symbols: [1]
2NO2(g) + 2H2O(g)
2 × ΔH1 + 2 × ΔH2 = ΔH f [N2H4(l)] + ΔH3
∴ ΔH f [N2H4(l)] = 2ΔH1 + 2ΔH2  ΔH3 [1]
(c) N2H4(l) + 2H2O2(l)  N2(g) + 4H2O(g) [1]
(d) Oxygen is reduced because its oxidation number decreases from –1 to –2. [1]
7. (a) (i)
(ii)
(iii)
Excess NaHCO3 added is to remove the acid catalyst [1] in order to quench
the reaction. [1]
Pipette [1]
The reaction mixture can be poured into ice-cold distilled water to slow down
the reaction progress. [1]
(b) (i)
(ii)
Copper electrode A dissolves/becomes thinner/becomes smaller [1]
For every Cu2+(aq) ion discharged at the copper electrode B, one is formed
from the copper electrode A. [1] Therefore, the concentration of Cu2+(aq) ions
does not change. [1] The intensity of blue colour of the solution remains
unchanged.
P.4
8. (a)
(i)
(ii)
(b)
Mg(OH)2 + 2H+  Mg2+ + 2H2O or Mg(OH)2 + 2HCl  MgCl2 + 2H2O [1]
CaCO3 + 2H+  Ca2+ + CO2 + H2O or CaCO3 + 2HCl  CaCl2 + CO2 + H2O [1]
Magnesium hydroxide is better because it does not produce gas when reacted but
calcium carbonate does. [1]
Chemical knowledge (Max. 4)
Treatment of industrial waste [1]

Industrial wastes are often acidic/ should be neutralized before disposal/ to reduce
water pollution
adding slaked lime/sodium carbonate to the acidic waste before discharge [1]
OR Making fertilizers



many common fertilizers are made by neutralization [1]
ammonium nitrate is manufactured by the neutralization of nitric acid with
ammonia/ HNO3(aq) + NH3(aq)  NH4NO3(aq) [1]
OR Adjustment of pH of soil for the growth of plants [1]

acidic soil is neutralized by adding slaked lime [1]

alkaline soil is neutralized by ammonium sulphate
OR Any other suitable examples [2]
Effective communication [1]